1. Field of the Invention
The present invention relates to a shutter device for a camera and, more particularly, to a shutter device for a camera, which can effectively provide an operating space of a shutter blade and a light-amount adjuster, improve assemblability of a top cover, and improve mechanical stability according to the assembly of the top cover by modifying the geometry of the top cover.
2. Description of the Related Art
As well known in the art, shutters for cameras are divided into two types: a lens shutter located close to a photographic lens and a focal-plane shutter located immediately before a film or a CCD.
The lens shutter is configured such that a circular exposure aperture is opened and closed, and in general, the exposure aperture is opened from the center thereof and closed toward the center by a plurality of shutter blades. Moreover, a lens shutter having a single shutter blade is also available in which the exposure aperture is opened from a predetermined periphery thereof and dosed toward the periphery after fully opened.
Meanwhile, a camera generally has a light-amount adjustment mechanism placed close to a photographic lens. Such light-amount adjustment mechanisms commonly used are called diaphragm mechanisms, which are of two main types. One is configured such that a plurality of shutter blades are rotated simultaneously in the same direction or rotated simultaneously in an opposite direction, and the diameter of the aperture can be continuously changed with respect to the optical axis by the cooperation of these blades. The other is configured such that, by providing a stop member with at least one circular aperture which is smaller in diameter than the exposure aperture or a plurality of stop members with a single aperture, the aperture can be selectively introduced into a photographing optical path.
In addition to the diaphragm mechanisms, mechanisms using neutral density (ND) filters are available for the light-amount adjustment mechanisms. In this case, there are those in which one ND filter having a predetermined density is introduced into the exposure aperture and those in which a plurality of ND filters different in density are provided and selectively introduced into the exposure aperture. In the mechanisms using the ND filters, there are those combined with the diaphragm mechanisms of the latter type, of the diaphragm mechanisms of the above two types. As an example, a circular aperture smaller in diameter than the exposure aperture is covered with the ND filter, and this covered aperture is introduced into the exposure aperture. Such a light-amount adjustment mechanism is suitable for the case where it is desirable that the influence of diffraction is excluded because the amount of light from an object can be materially reduced without extremely diminishing the aperture.
As discussed above, the lens shutter mechanism and the light-amount adjustment mechanism are not located immediately before the film or the CCD, but close to the photographic lens. Thus, in a camera provided with these two mechanisms including the lens shutter mechanism and the light-amount adjustment mechanism, it has been common practice to manufacture the two mechanisms as one unit. Examples of this configuration are set forth in detail in Japanese Patent Publication No. 2001-117135 and Korean Patent Publication No. 10-2009-0012497.
Meanwhile, the camera shutter device having a structure in which the lens shutter mechanism and the light-amount adjustment mechanism are simultaneously employed in the above camera has a shutter assembly comprising a shutter base having an aperture for incident light, shutter blades for blocking incident light, a blade driving unit for rotating the shutter blades, aperture blades for adjusting the amount of incident light, a driving unit for driving the aperture blades, a shutter plate for dividing a space in which the shutter blades and the aperture blades can move, and a shutter cover for protecting them. During assembly of the shutter cover, an adhesive is applied to a step height formed across the inner circumference of the shutter base on which the shutter cover is to be placed such that the shutter cover is attached and fixed thereto.
However, according to the above-described shutter cover assembly structure, when the shutter cover is assembled to the shutter base, the adhesive is applied to the entire circumferential surface of the shutter base, and then the shutter cover is attached thereto. Thus, the assembly operation is cumbersome and requires more assembly time. Moreover, the adhesive penetrates into the shutter base to affect the mechanical operation of the shutter device. Furthermore, since the shutter cover is fixed to the shutter base only using the adhesive, the adhesion of the shutter base is low, and thus the shutter cover may be separated from the shutter base. In addition, since the shutter cover is in contact with the edge of the shutter base and fixed thereto, the inner part of the shutter cover is vulnerable to deformation, and thus it may cause interference with the operation of the shutter blades or the aperture blades.